1. Field of the Invention
The present invention relates to a novel composition for metallizing surfaces of ceramics such as aluminum nitride, alumina and silicon nitride, a method of metallizing ceramic surfaces by using this composition, and a surface-metallized ceramic article formed by utilizing these composition and method.
2. Description of the Related Art
Only where at least several % of an SiO.sub.2 component is contained has a method of metallizing a ceramic surface by baking a mixture of Mo, Mn and a frit component at a temperature of 1300.degree. to 1600.degree. C. in wet hydrogen, i.e., the Mo-Mn method, been adopted, but although a metallizing composition applicable to a high-purity ceramic sintered body in which the content of the glass phase in the crystal grain boundary is low, i.e., alumina, aluminum nitride or silicon nitride having a purity of at least 99%, has been developed. there is still room for a further improvement thereof.
For example, a composition of the Cu-Ag-Ti system is a usual metallizing composition applicable to alumina and aluminum nitride, and if the Ti content is reduced to less than 5% in this composition, the metallized pattern is disturbed or pinholes are readily formed, and if the Ti content is increased, the metallized layer becomes hard and is easily broken because of the different thermal coefficients of expansion of the ceramics. A composition of the Pd-Ta-Zr-Mn-Ni-Cu system as disclosed in Japanese Unexamined Patent Publication No. 63-60186 can be mentioned as the metallizing composition applicable to aluminum nitride, but since scores of % of Pd, which is a noble metal, and an expensive Ta are contained in the composition, the metallizing composition of this type is very costly.
A composition of the Nb-Cr-Zr-C-Si-SiC-Ni system as disclosed in Japanese Unexamined Patent Publication No. 61-014181 can be mentioned as the metallizing composition for silicon nitride, and this composition is practically used in various fields, but since the metallization is effected at a high temperature exceeding 1200.degree. C., in the case of a sintered body having a high content of a sintering aid such as Y.sub.2 O.sub.3, the grain boundary containing Y.sub.2 O.sub.3 is quickly deteriorated, and thus many problems remain to be solved.